Skin care compositions contain a variety of additives that provide a wide array of benefits to the composition. Sunscreen compositions in particular contain additives that offer protection from ultraviolet (“UV”) radiation, which can damage the skin. UV radiation can be classified as UVA (long wave; i.e., wavelengths of 320-400 nm) and UVB (short wave; i.e., wavelengths of 290 to 320 nm). The efficacy of sunscreen formulations is measured by its sun protection factor (“SPF”). Since both UVA and UVB forms of radiation are harmful, sunscreen formulations offer protection from both kinds of rays. Inorganic metal oxide particles, such as titanium dioxide and zinc oxide, provide absorption of UVA and UVB radiation and to this end are commonly incorporated into sunscreen formulations. Inorganic metal oxides, however, can cause negative aesthetic qualities such as poor sensorial feel and an undesirable white appearance, both of which may be due to agglomeration of particles and poor distribution on skin.
Durability of sunscreen formulations is another consideration that has been addressed in the art. For example, U.S. Pat. No. 6,384,104 discloses UV radiation absorbing compositions containing a latex for the purpose of maintaining storage stability of sunscreen formulations when added to personal care compositions. The prior art does not, however, disclose a formulation containing inorganic metal oxide particles and copolymer particles according to the present invention which gives superior results as a UV absorption booster.
Accordingly, there is a need to develop new sunscreen compositions including sunscreen boosters which will help provide a high SPF, while improving aesthetic qualities of such formulations such as sensorial feel and visual appearance.